The present invention is a capacitor comprising: an electrically-conductive porous substrate having a porous part; a dielectric layer positioned on the porous part; and an upper electrode positioned on the dielectric layer. The capacitor is characterized in that: at least 5% of the total porous part of the electrically-conductive porous substrate consists of a section having a substrate thickness, between pores, that is no more than 1.2 times the thickness of the dielectric layer; and the dielectric layer is formed from a compound comprising atoms not derived from the electrically-conductive porous substrate.
